Helicobacter pylori (previously Campylobacter pylori) is a spiral bacterium that was cultured from the human gastric mucosa in 1982. Various studies have indicated that the presence of H. pylori is strongly associated with chronic (Type B) gastritis. H. pylori colonization is usually chronic in nature. If the organisms are eradicated, the histological inflammation improves. When the organisms reappear, inflammatory changes recur. These findings have favored the theory that chronic colonization by H. pylori causes Type B gastritis. Even though there is histological inflammation, symptoms are frequently not present. The presence of H. pylori has also been associated with gastric and duodenal ulcers. The organism is present in 95-98% of patients with duodenal ulcers and 60-90% of patients with gastric ulcers. A person with gastrointestinal symptoms with evidence of H. pylori colonization (i.e. presence of specific antibodies, positive breath test, positive culture or positive biopsy) is considered to be infected with H. pylori. A person without gastrointestinal symptoms having evidence of the presence of the H. pylori organism is said to be colonized, not infected. It is not clear whether H. pylori has an etiological role in ulcer formation or if it has a commensal association. Studies have demonstrated that removal of the organism by antimicrobial therapy reduces the risk of peptic ulcer recurrence.
Traditionally, the presence of H. pylori has been detected through biopsy. The biopsy is obtained by endoscopy. As with any invasive procedure needing some form of sedation, some risk and discomfort to the patient is present. Detection of the organism involves culture of the gastric biopsy specimen, examination of stained biopsies for the presence of bacteria, or detection of urease activity in the biopsies themselves. Biopsy by endoscopy may lack some sensitivity due to the patchy nature of H. pylori colonization. Noninvasive methods include a urea breath test, which utilizes radioactive isotopes and is still under investigation for clinical use, and serology. The presence of H. pylori specific antibodies in human serum has been shown to be an accurate indicator of H. pylori colonization.